Bicarbonate is an anion that has an important role in acid-base balance. Bicarbonate measurement in urine is not routinely performed. Urine pH and urine anion gap are the recommended tests for the evaluation of suspected urine bicarbonate loss. As such, requests for urine bicarbonate will be reflexed to measurement of urine anion gap.
Ambient (8 - 24 degrees Celsius)
It is rarely necessary to measure bicarbonate in urine. It is recommended that you discuss with a chemical pathologist before requesting this test.
In normal health, almost all the filtered bicarbonate is reabsorbed (90% in proximal nephron, 10% in distal nephron) and so the urine is almost entirely free of bicarbonate.
Bicarbonaturia is associated with type II renal tubular acidosis. However the preferred test for investigation is urine anion gap (type II RTA is associated with a negative urine anion gap). Requests for urine bicarbonate will be changed to urine anion gap by the lab, unless discussed with a pathologist.
Please note that the bicarbonate assay has not been validated for measurement on body fluid specimens. Results must be interpreted with caution.